WIND TUNNEL

The Tatuus wind tunnel facility project born in the year 2005 to step forward a better aerodynamic performance of racing cars.
The complete design of the tunnel and its subsystem has been carried out by Tatuus technical department having set as main targets the dimension of the plant, the scale of the model and the flow speed.

SPECIFICATIONS

The windtunnel has a "closed return" architecture in order to have a better flow quality in terms of uniformity and properties, in fact the air flowing into the tunnel is mostly the same and can be kept at the same temperature and humidity during test session.
Moreover "closed return" is not influenced by external condition (like entry flow asymmetries), finally the contraction ratio 7:1 reduce turbulence scales and flow misalignments.

The duct measures 75 metres length and contains 473 m^3 of air flowing at 60m/s in the test section.
A combination of screens and honeycomb together with the contraction ratio provide a superior flow quality in terms of uniformity of velocity, direction and turbulence.

A wide study based on numerical simulation (CFD- Fluent) has been done to optimise the efficiency of the tunnel, special attention has been focused on the fan-straightener and the corner turning vanes to avoid any possible power losses due to swirl velocity and turbulence.

The axial fan straightener is located in the return arm of the tunnel, it measures 2.5m diameter and is powered by an electric motor of 120kW, its task is to raise the static pressure of the flow that will be transformed in air speed throughout the nozzle.
The fan-straightener have 6 rotating carbon blades followed by 5 static, the design and manufacturing has been done by Tatuus and allow a reduction of inertia, a very controlled shape of profiles and not least a great stiffness under the aerodynamic stress.
The rev speed is controlled by an hydraulic transmission managed by software in order to maintain the requested speed.

The cooling subsystem is another crucial component of the tunnel, the heat-exchanger is located in the slowest part of the tunnel to minimize pressure losses and increase the heat transfer efficiency. The chiller unit prevent any temperature build-up during testing within a range of 1¡C to maintain the air properties constant and have the better measurement repeatability.

TEST SECTION

The test section measures 1.7 x 1.2 metres and can accommodates models up to 35% scale and is equipped with a rolling road that can achieve 60m/s.
Two suction stages aspire the boundary layer to virtually erase the thickness of slow air that flows close to the walls, ceiling and side walls are equipped with static port to monitor flow blockage in the test section.
Rolling road speed is software controlled to follow wind speed and simulate the track moving under the chassis.
Moreover the wheels are moved by the belt and rotating they reproduce the real condition of the running vehicle.
Rolling belt is sucked by a porous plate to counteract the suction of the vehicle underfloor, 5 vacuum area permit to control this suction and reduce the friction.
Moreover the plate where the belt slide is water cooled to increase belt lifespan, the four wheel position are constantly monitored for temperature.

The scaled model is hung over a carbon strut and is not connected to wheels to avoid any possible force interaction and vibration noise coming from the moving road.
A 6 component internal balance is installed inside the model, it facilitates the measurement of lift, drag and side forces, along with their moments of yaw, roll and pitch.
The balance is mounted on an independent structure to eliminate vibration from the tunnel structure.
Four more balances are in charge of the wheel drag measurement.

The model's attitude can be continuously controlled during run session by software, ride height and pitch angle can be adjusted to provide a complete aero map without stop to the air flow.
Laser position sensor are in charge to close the control loop.

In terms of sensor and measurement capabilities the heart of the system is the 6 component Aerotech internal balance, in addition 16 static ports, plus 24 on the only test section, monitor the flow around the tunnel's circuit, 4 temperature sensor send data for thermal control.
A traversing system can made a very precise positionment of several flow measurement device like directional probes, boundary layer rakes, pitot tubes.